This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A087515 #10 Sep 21 2024 12:22:31 %S A087515 19,11919199,11919991,19111999,19199119,19911919,19991911,91919911, %T A087515 91999111,99111919,99119191,99919111,1111919999,1111999199,1191911999, %U A087515 1191919991,1191991991,1191999119,1199911919,1199911991,1199919191,1199919911,1911919199,1911991919 %N A087515 Primes consisting only of digits 1 and 9 occurring with equal frequency. %C A087515 There are 18 digit pairs which can produce such primes. (1,0),(1,3),(1,4),(1,6),(1,7),(1,9),(2,3),(2,9),(3,4),(3,5),(3,7),(3,8),(4,7),(4,9),(5,9),(6,7),(7,9),(8,9). %H A087515 Andrew Howroyd, <a href="/A087515/b087515.txt">Table of n, a(n) for n = 1..10477</a> %o A087515 (PARI) \\ Needs B() from A087510. %o A087515 concat(vector(6,k,B(k,1,9,isprime))) \\ _Andrew Howroyd_, Sep 21 2024 %Y A087515 Cf. A087510, A087511, A087514. %K A087515 base,nonn %O A087515 1,1 %A A087515 _Amarnath Murthy_ and _Paul D. Hanna_, Sep 11 2003 %E A087515 Offset changed and a(22) onwards from _Andrew Howroyd_, Sep 21 2024